new gauges but with cruise control

[nbesheer]

I read on http://www.zcarparts.com that their 140MPH speedometer is the only one that works with cruise controls but i find that hard to believe so when looking at gauges what do I need to look for that enables them to work with cruise control ? just like cruise control supported ? I don't' see anything like that on autometer

[zcarnut]

The 280ZX cruise control “sensor†is nothing more than a reed switch. A reed switch contains two metal contacts (the “reedsâ€) which are sealed in opposite ends of a small glass tube. A magnetic field in close proximity will cause the contacts to pull together to complete the electrical circuit. The stiffness of the reeds causes them to separate to open the circuit when the magnetic field ceases:

 

http://www.reed-sensor.com/Notes/Magnet_Applications.htm

 

The reed switch uses the magnetic field generated by the spinning permanent magnet that is already in the speedometer. This magnet is spun by the speedo cable and induces a voltage in the meter movement of the speedometer. [The faster the magnet turns, the higher the induced voltage, Faraday's law of induction, and the more the speedometer needle moves.] So, the only difference with the ZX “cruise control†speedo is that it has the reed switch.

 

When I transplanted a 280ZX cruise control system into my Datsun 810 I mounted a ZX reed switch in the 810’s speedometer with epoxy. I got the reed switch from a junk ZX speedo.

 

You may be able to accomplish the similar feat with an aftermarket speedometer, but is has to have the spinning magnet (analog meter movement). If the new speedometer is “digital†(more common nowadays) then you can’t use a reed switch with it.

[Warren]

If you choose not to use the ZX Speed Sensor (reed switch) you'll need a speedometer cable driven speed sensor, commonly used on GM products (available from JTR as well as Summit, amongst other places). The ZX speed sensor provides 2 pulses per revolution. If you're wiring this into a ZX, the below diagram applies. The YW wire is the one to put one lead to and the YL is the other...the YL connects to ground in the body harness if that helps.

 

YW - Yellow White, YL - Yellow Blue

 

 

Hope that helps clear up with wiring of it.

 

NOTE: If your car is equipped with "Bitchin Betty", this little fix will get her fully working again if you've changed to the 140mph Speedometer and lost some of her messages (the ones requiring the car to be moving, like Door Ajar, Park brake is set, etc). This also works if you've changed to aftermarket gauges.

[HizAndHerz]

Some cruise control systems use a magnet that is attached to the driveshaft with the sensor mounted off the tunnel wall. Adding a second magnet to the opposite side of the driveshaft would provide the 2-pulses per revolution required by the ZX.